Lithium base grease



Unite States Patent Office 2,842,494 Patented July 8, 1958 LITHIUM BASEGREASE Richard A. Butcosk, East Heinpstead, N. Y., assigno'r to SoconyMobil Oil Company, line, a corporation of New York No Drawing.Application November 20, 1956 Serial No. 623,318

13 Claims. (Cl. 252-36) This invention has to do with greasescharacterized by a high order of effectiveness over a wide range ofoperating conditions. More specifically, the invention is related tolithium base lubricating grease compositions which possess outstandingmechanical stability when worked in the presence of excess water.

This application is a continuation-in-part ofmy copending applicationSerial No. 409,760, filed February 11, 1954, which has been abandoned.

In recent years, a demand has been created for greases of outstandinglubricating character which retain their grease structure during useover a wide range of operating conditions. For example, there has beenan increasing demand for water-resistant greases by the military and bysuch industries as steel mills, paper mills and food canning. Untilrecently, lithium stearate greases have been sufficientlywater-resistant to meet specifications announced by the military andindustry. Now, however, specifications have been made more stringent inorder that excellent lubricating performance be assured in service.

Lithium stearate greases have been designated as waterresistant orwater-repellant, in accordance with their evaluation in the waterwashout test (specification ANG-Sa) and the water-resistant test(specification O. S. 1350). A more severe water test, more recentlyannounced, is that involving admixture of of water with the grease andworking the resulting mixture in a motor-matic worker for 100,000 doublestrokes. This test is fully described in the military specification MIL-G-l0924, Amendment 2. Conventional types of lithium soap greases,particularly lithium stearate greases, work to a semi-fluid condition inthis latter test. A number of steps have been taken to increase thewater resistance of such greases. For example, free fat, such as hightiter animal tallow, has been incorporated in the grease for thispurpose. This approach appears to be disadvantageous or deleterious inother respects in that the fat is unstable and generally decomposes intofatty acids and glycerin, such that the grease eventually softens instorage and also in service. Other additives such a'szinc naphthenateand zinc resinate, have been used in greases to improve thewater-resistance characteristics, but they, too, soften with water.

It is an object of this invention, therefore, to provide a grease whichretains its original character over a wide range of operatingconditions. A primary object of the invention is to provide a greasecomposition characterized by excellent mechanical stability oflubricating quality and of grease-like structure, when worked in thepresence of excess water. Other objects of the invention will beapparent from the following description:

These and other objects have been realized by formation of new and novellithium base compositions, which contain mixtures of lithium soaps inwhich the acid components of the soaps comprise balanced proportions ofwool grease fatty acids and aliphatic acids having at least about 12carbon atoms per molecule, The same objects are also realized by formingmixtures of lithium and sodium soaps, lithium and potassium soaps, andof lithium and tin soaps, of said acids, in which mixtures balancedproportions of lithium and sodium, lithium and potassium, and lithiumand tin, respectively, are main- 'tained.

Wool grease fatty acids are well known in the art. For example, theyhave been described in detail by E. S. Lower in the Industrial Chemist,in the March, May and October issues of 1947. As defined in theaforesaid publication, wool grease fatty acids are those fatty acidswhich are obtained when the soap solutions obtained in the manufactureof lanolin are acidified, may be extremley pale in color, or may be verydark to almost black, and may be nearly free from odour or have a strongacidic smell. They range from soft, limpid compositions to hard,wax-like materials, the latter usually being a paler product.

As further explained in the aforesaid publication, Wool grease fattyacids are composed, generally speaking, of the fatty acids obtained fromthe scouring liquids used in washing the wool in textile mills, and alsothe natural free wool wax acids and neutral saponifiable matter. Theymay also contain, depending upon the care taken in their manufacture andfinish, traces of undecomposed soap from the manufacture of wool wax,and also traces of water soluble salts, mainly sodium sulfate, and alsoe'ven traces of free sulfuric acid used in the decomposition of'the'above-mentioned soap.

Physical characteristics of wool grease fatty acids, and of a typicalwool grease fatty acid product, are illustrated below in the followingtabulation:

PHYSICAL CHARACTERISTICS oi wooL GREASE FATTY ACIDS Range TypicalMoisture .percent 1-5 2 Unsaponlflable. do A 3-7 5 Saponlfiable, do. -98Free Fatty Acids, as Oleic d0 70-95 84 Free Neutral Fat .do. 0-5 NoneSaponification Value -190 170 Iodine Value; 20-50 25-34 Titer 40-4540-43 The above tabulation is descriptive particularly of wool greasefatty acids as produced in the United Kingdom. More recently in the U.S. A., with the advent of the 'recovery'of lanolin alcohols andcholesterol from degras, wool grease fatty acids of somewhat differentphysical and chemical characteristics are available, and are a preferredmaterial.

U. s. A. WOOL GREASE FATTY ACIDS RECOV- ERED AS A BY-PRODUCTOFLANOLINHALCO- HOLS AND CHOLESTEROL MANUFACTURE Acid number 105-125Saponification number -165 Iodine number (Hanus) 10-20 Titer, "C- t50-53 Acetyl number 45-75 Water percent 1-3 Typical of such materialsare vegetable, animal andfish fatty oils, and hydrogenated fattymaterials thereof, such as stearin, hydrogenated tallow fatty acids,hydrogenated soya bean fatty acids, hydrogenated fish oils and partialhydrogenated marine, vegetable, and animal oils. Preferred herein,together with the wool grease fatty acids, are stearic acid and palmiticacid, and myristic acid. A particularly outstanding grease is obtainedwith balanced proportions of wool grease fatty acids, stearic acid andhydroxy stearic acid.

One of the most critical relationships involved in the formation of thelithium-lithium base greases of this invention, is the balancedproportion of the lithium soap acid components. It has been found thatthe desired waterresistant characteristic is obtained only by using fromabout percent by weight to about 80 percent by weight of wool greasefatty acids, with the remainder of the :acid components comprisingaliphatic acids of the character described above. Outstanding greasecompositions are obtained when the balance of acid components comprisesfrom about 25 percent by weight to about 50 percent by weight of woolgrease fatty acids, with the remainder being the aforesaid aliphaticacids. For example, when lithium soaps of wool grease fatty acids aretotally absent from corresponding lithium base grease compositions, thelatter have unsatisfactory waterresistant characteristics. Even when thelithium soaps of wool grease fatty acids are present in combination withother lithium soaps, such as lithium stearate, but in inadequateproportions, the resulting compositions are found to be unsatisfactory.Such a grease composition is one wherein the lithium soaps of woolgrease fatty acids represent less than about 15 percent by weight oftotal fatty acid content. Another feature to be noted is a greasecontaining only lithium soaps of wool grease fatty acids, is inferior togreases of this invention; that is, such a grease sets up in prolongedstorage or in other words, the grease becomes much firmer in consistencysuch that it fails to lubricate properly when used.

The finished lithium-lithium greases can be somewhat acidic, somewhatbasic in reaction or can be neutral. That is, the finished greases cancontain acid equivalent to as much as 0.5 percent by weight of oleicacid, or can contain alkali equivalent to as much as 0.2 percent byweight of lithium hydroxide. correspondingly, the lithium-sodium,lithium-potassium and lithium-tin greases can also be acidic, neutral orbasic; and substantially the same limits of acidity and alkalinityobtain. As indicated above, mixtures of lithium and sodium soaps of theforegoing acids are also contemplated herein. When such mixtures areused, the mole ratio of lithium to sodium (Li:Na) of the lithium andsodium compounds used in the pre-formed soaps or the soaps formed insitu will be between about 15:1 to about 3: 1, with preference beinggiven to ratios within the range of about 6:1 to about 4: 1.

Contemplated herein also are mixtures of lithium and potassium soaps ofthe foregoing acids. The ratio of lithium to potassium (LicK) of thelithium and potassium compounds used in the preformed soaps or the soapsformed in situ will be between about 50:1 to about 10:1; preferredratios are those from about 40:1 to about :1.

Also indicated above as coming within the bounds of this invention aremixtures of lithium and tin soaps. The ratio of lithium to tin (LizSn)of the lithium and tin compounds used in the preformed soaps or thesoaps formed in situ varies from about 5021 to about 8:1; preferredratios range from 30:1 to about 20:1.

It is to be understood that mixtures of lithium soaps with more than onesoap of the other metalssodium, potassium and tincan be used. That is,the final composition can contain lithium, sodium and potassium soaps;lithium, potassium and tin soaps; lithium, sodium and tin soaps;lithium, sodium, potassium and tin soaps. In such mixtures, the balanceof acids defined above is main tained. Similarly, .the mole ratio oflithium to other metals will fall within the bounds indicated above.

The total quantity of soaps (lithium and lithium; lithium and sodium;lithium and potassium; lithium and tin; etc.) is also balanced in orderto provide greases of the desired character. The soaps comprise fromabout 5 to about 30 percent (by weight) of the finished greases, andpreferably from about 7 to about 20 percent.

Inasmuch as methods for the preparation of lithium, sodium, potassiumand tin soaps, and greases containing the same, are well known in theart, discussion of the same is believed to be unnecessary here. It is tobe understood, however, that preformed soaps can be incorporated in oilto make the greases; and that the soaps can be formed in situ.Illustrative examples, however, are furnished hereinbelow as a guide.

It will be understood also that a variety of lithium, sodium, potassiumand tin compounds can be used in preparing the soaps present in the newgrease compositions. For example, lithium compounds such as thehydroxide, carbonate and hydride can be used. Typical of the sodium andpotassium compounds useful herein, in addition to the individual metals,are the carbonates and hydroxides. Of the tin compounds which are usefulherein, the stannous halides are advantageous in effecting doubledecomposition; of these, stannous chloride is preferred.

The mineral oil constituent of the greases of this invention can be ofvaried character. The oil constituent, is characterized by a viscosity(SUV) of greater than one second at 100 F., and generally from about 60to about 6000 seconds at 100 F. The oil may be of naphthenic or ofparafiinic character. Typical oils are a naphthenic mineral oil, havinga SUV of 70 seconds at 100 F., and a solvent-refined, naphthenic oilhaving a SUV of 80 seconds at 100 'F.

Grease compositions of this invention may be pre pared from preformedsoaps, or the soaps may be made in situ in a grease-forming base of thecharacter described above. It will be clear that when the soaps areprepared in situ by a procedure such as that illustrated below, therewill be formed a mixture of wool grease fatty acid soaps and of theaforesaid aliphatic acid or acids, with the metals used beingdistributed between the said acids. Obviously, when only lithium soapsare involved, the mixture will comprise lithium wool grease fatty acidsoaps and one or more lithium soaps of one or more aliphatic acids.Where a mixture of lithium and sodium soaps are desired, then theresulting mixture will comprise: lithium wool grease fatty acid soaps, alithium soap or soaps of the aliphatic acid or acids, sodium wool greasefatty acid soaps and a sodium soap or soaps of the aliphatic acid oracids. correspondingly, when the mixture to be formed 18 one of lithiumand potassium soaps or lithium and tin soaps, the distribution of soapswill correspond .to that in the case of lithium and sodium mentioneddirectly above.

It has been found, however, that in preparing the grease compositions ofthis invention from preformed soaps, a lithium soap of the aliphaticacid (i. e. other than lithium wool grease fatty acid soap) must bepresent. Or, expressed in another manner, at least some of the woolgrease fatty acid soap present must contain lithium, sodium, potassiumor tin. This feature is demonstrated hereinafter by a comparison ofgreases made with preformed soaps; the grease made with sodium stearateand lithium wool grease fatty acid soap is so different (so poor) inwater-resistance or water-repellancy that it is outside the scope ofthis invention.

A typical procedure for preparing the greases, in situ, is thefollowing. All of the fatty materials, wool grease fatty acids and, forexample, hydrogenated tallow fatty acids and 3040 percent of the totalmineral oil, are charged to a suitable grease kettle. The resultingmixture is heated to about 140460 F, and then the required proportion oflithium hydroxide monohydrate dissolved in water, is added. -This isfollowed by addition of a water rinse. After this, the mixture soobtained is heated to- 380-390 F., o; :r a period of one to three hoursAt this point, .the balance of mineral oil used in preparing the greasecompositions, is added, and the total mass is reheated to 390-400 F. fora period of one to two hours. The resulting liquid product is withdrawnfrom the grease kettle into pans for cooling to room temperature (70-80F.), which cooling generally requires two to ten hours. The cooledblocks of grease which are so obtained, are milled to a buttery productof the desired penetration.

Grease compositions of this invention have been compared withconventional lithium stearate and lithium hydroxy stearate greases, bysubjecting said greases to the test described in military specificationMIL-G-10924, amendment 2. As indicated earlier, this test involvesworking the greases with percent by weight of water, in a Motor-MaticWorker for 100,000 double strokes.

The results of these tests are tabulated below in Table I.

Table l A typical procedure for preparing a grease containing lithiumand sodium soaps, isthe following:

All of the fatty materials, wool grease fatty acids and stearic acid and-40 percent of the total mineral oil are charged to a suitable greasekettle. The resulting mixture is heated to about 140-160 F., and thenthe required proportions of lithium hydroxide monohydrate and sodiumhydroxide, dissolved in water, are added. This is followed by additionof a water rinse. After this, the mixture so obtained is heated to380-390" R, over a period of one to three hours. At this point thebalance of mineral oil used in preparing the grease composition, isadded, and the total mass is reheated to 390-400 F. for a period of oneto two hours. The resulting liquid product is withdrawn from the greasekettle into pans for cooling to room temperature (7080 R), which coolinggenerally requires two to ten hours. The cooled blocks of grease whichare so obtained, are milled to a buttery product of the desiredpenetration.

Hydrogenated Tallow Fatty Acids, Percent Hydrogenated Soya Bean FattyAcids, Percent. 12 Hydroxy Stearic Acid, Percent 8. 00 9. 50 Wool GreaseFatty Acids, Percent 3. 85 8.50 3.00 1.50 fithiunliglylrdrlgxidtelfilionohygragvPercerg r 1. 1. 70 1. 55 1. 65 1; 50 1. 35

inera a chic 7 S at 1 Percent .2 .i s9. 00 89. 15 86. 87. 45 87.35 89.0089. 15 Penetration (Unworked) at 77 F 300 230 260 250 300 2 300 WorkerTest (100,000 with 10% water), 420+ 321+ 308 345 379 365 420+ Review ofthe data tabulated above in Table 1, reveals that grease composition 1,which contains no lithium soap of wool grease fatty acids, ischaracterized by poor waterresistance. This is seen by the value 420+. Asimilar result is found for grease composition 7; this grease containsonly a lithium soap of 1'2hydroxy stearic acid. In contrast, grease.compositions 2 through 6 are all of excellent water-resistancecharacter. Each of the latter greases is formulated from balancedproportions of wool grease fatty acids and other acids. In the lattergreases, thev percentage of wool grease fatty acids ranges from about 15percent to about 80 percent of the total acid components of the lithiumsoaps.

Additional greases illustrating those of this invention, are shown belowin Table H. These greases are shown in a solvent-refined mineral oil incontrast to the naphthenic mineral oil vehicle used in the greases ofTable I.

Table II.-S0lvent-refined mineral oil 80" at 100 F.

Hydrogenated Tallow Fatty Acids, percent. 8. 00 8. 00 8.00 Wool GreaseFatty Acids, percent 3. 85 2. 75 2.00 Lithium Hydroxid e-Monohydrate,percent... 1. 70 1. 57 1. 48 MineralOil, 80 SUV at 100 F., percent 86.45 87. 68 88. 52 Pan Cooled Yes Yes Yes Penetration at 77 F. (Unworked)305 207 300 Worker Test (100,000XK with 10% HzO) 287 346 373 Stillfurther greases of the character contemplated herein, are those shownbelow in Table III. Here the oil vehicle is an acid-treated andsolvent-treated mineral oil of higher viscosity than of the oils usedshown in Tables I and II.

Table III.Acid-treated and solvent-treated mineral oil A lithium-sodiumgrease composition (13) of this invention is shown below in Table IV.

Table IV Stearic acid, percent 8.00 Wool grease fatty acids, percent3.00 LiOI-LH O, percent 1.63 0.30

NaOI-I, percent Mineral oil (solvent-refined, 500 SUS F),

percent 87.07 Penetration (unworked) 270 Worker test (l00,000 with 10% HO)- 350 A typical procedure for preparing a grease containing lithiumand potassium soaps is much the same as that given above for thelithium-sodium grease. The only change made is in the use of potassiumhydroxide in place of sodium hydroxide.

Representative of the lithium-potassium soap greases is that shown (14)in Table V below.

Table V Lithium-tin grease compositions can be prepared by the followingprocedure:

Heat the fatty materials and about 30-40% of the mineral oil to F. andadd the LiOH dissolved in water, and the dry tin stearate. Heat and stirto dehydrate the mixture of a temperature of 400 F. Add the balance ofthe mineral oil in two portions and each time reheat the mixture to 400F. Allow the product to cool to room temperature. The cooled block ofgrease is then milled to a buttery product of the desired penetration.

A lithium-tin grease composition (15) of the invention is illustratedbelow in Table VI.

Table VI Stearic acid, percent 7.00 Wool grease fatty acids, percent3.00 LiOHH O, percent 1.60 Tin di-stearate, percent": 1.00

Mineral oil (solvent-refined, 500 SUS 100 F.),

percent 87.40

Penetration 77 F. (unworked) 261 Worker test (100,000X A with H percent302 As indicated above, grease compositions of the type contemplatedherein can be prepared with preformed soaps. Conventional procedures canbe used when making use of the preformed soaps. The illustrative greasecompositions shown below were prepared in the following manner.

The wool grease fatty acid soap was mixed with about thirty percent (byweight) of the total mineral oil; the mixture was heated to about 400F., and the resultant mixture was cooled. The conventional aliphaticacid soap (i. e., the stearate) was mixed with about thirty percent ofthe total mineral oil; this mixture was heated and cooled in likemanner. The two soap mixtures were then combined with each other andwith the remainder fatty acids and the balance of said acid componentscomprising aliphatic acids having at least about twelve carbon atoms permolecule, the metal components of said'soaps being selected from thegroup consisting of lithium and lithium, lithium and sodium with themole ratio of lithium to sodium being between about 15:1 and about 3:1,lithium and potassium with the mole ratio of lithium to potassium beingbetween about 50:1 and about 10:1, and lithium and tin with the moleratio of lithium to tin being between about 50:1 and about 8:1;preformed soaps of said mixtures of lithium-sodium, lithium-potassiumand lithium-tin soaps comprising a lithium soap of said aliphatic acidand wool grease fatty acid soaps of said metal other than lithium.

2. A grease "defined by claim 1 wherein the mixture of soaps is formedin situ in the mineral oil.

3. A grease defined by claim 1 wherein the mixture of soaps is a mixtureof preformed soaps.

4. A grease defined by claim 1 wherein the proportion of said mixture ofsoaps is from about 5 to about 30 percent by weight of the grease.

5. A grease defined by claim 1 wherein the wool grease fatty acidscomprise from about twenty-five percent by of the oil; the resultingmixture was heated to about 400 F. The final product was cooled tom-80F.and, when so cooled, was milled to a product of the desired penetration.Grease compositions so prepared are shown in Table VII below.

Table VII.-Pref0rmed soaps Soaps 16 Sodium Stearate, percent LithiumSoaps of wool grease Fatty Acids, percent Lithium Stearate, percent- 1Pan cooled grease was striated which was separated into oil pockets Itis to be noted in Table VII that grease composition 16 is comprised ofsodium stearate and of lithium soaps of wool grease fatty acids, andthat it is characterized by unsatisfactory water resistance. In directcontrast, grease composition 17 has considerable water resistance; thiscomposition is comprised of lithium stearate and sodium soaps of woolgrease fatty acids.

it is to be understood that the greases of this invention can alsocontain other characterizing materials. For example, the greases cancontain grease antioxidants such as amines, phenols, sulfides, etc., andlubricity improving agents such as free fat, free fatty acids, esters ofalkyl and/or aryl acids, sulfurized fats, lead soaps, etc. Thesecharacterizing materials do not detract from the lubricating value ofthe greases contemplated herein; rather, these characterizing materialsserve to impart their customary properties to the grease. The amount ofsuch additives can be added to grease compositions of this invention inaround about 0.01 percent to less than 10 percent by weight, andpreferably 0.1 to 5.0 percent by weight. 1

Greases of this invention are applicable for general automotive uses,and are excellent aircraft greases, industrial greases and the like. a

I claim:

l. A lubricating grease comprising a major proportion of mineral oil anda minor proportion, sufficient to form a grease, of a mixture of soapsselected from the group consisting of preformed soaps and of soapsformed in situ in the mineral oil, the acid components of said soapscomprising from about fifteen percent by weight to about eighty percentby weight of wool grease components.

6. .A grease defined by claim 1 wherein the aliphatic acid is stearicacid.

7. A grease defined by claim 1 wherein the aliphatic acid ishydroXy-stearic acid.

8. A grease defined by claim 1 wherein the aliphatic acids comprise amixture of stearic acid and hydroxystearic acid.

9. A lubricating grease comprising a major proportion of mineral oil anda minor proportion, sufficient to form a grease, of a mixture of lithiumsoaps, the acid components of said soaps comprising about twenty-fivepercent by weight of wool grease fatty acids and about seventy-fivepercent by weight of stearic acid.

10. A lubricating grease comprising a major proportion of mineral oiland a minor proportion, sufficient to form a grease, of a mixture oflithium soaps, the acid components of said soaps comprising aboutone-third by weight of wool grease fatty acids and about two-thirds byweight of stearic acid.

11. A lubricating grease comprising a major proportion of mineral oiland a minor proportion, suificient to form a grease, of a mixture oflithium soaps, the acid components of said soaps comprising aboutone-fourth by weight of wool grease fatty acids and about threefourthsby weight of stearic acid.

12. A lubricating grease comprising a major proportion of mineral oiland a minor proportion, sufficient to form a grease, of a mixture oflithium and sodium soaps formed in situ, the acid components of saidsoaps comprising about one-third by weight of wool grease fatty acidsand about two-thirds by weight of stearic acid, the mole ratio oflithium to sodium being about 5:1.

13. A lubricating grease comprising a major proportion of mineral oiland a minor proportion, sufficient to form a grease, of a mixture oflithium and tin soaps formed'in situ, the acid components of said soapscomprising about one-third by weight of wool grease fatty acids andabout two-thirds by weight of stearic acid, the mole ratio of lithium totin being about 26:1.

References Cited in the file of this patent UNITED STATES PATENTS2,676,149 Woods et a1. Apr. 20, 1954 FOREIGN PATENTS 550,429 GreatBritain Jan. 7, 1943 7 OTHER REFERENCES Wool Wax, D. T. C. Gillespie,Hobart Pub. Co. Washington, D. C., 1948, pages 55 and 56.

1. A LUBRICATING GREASE COMPRISING A MAJOR PROPORTION OF MINERAL OIL ANDA MINOR PROPORTION, SUFFICIENT TO FORM A GREASE, OF A MIXTURE OF SOAPSSELECTED FROM THE GROUP CONSISTING OF PREFORMED SOAPS AND OF SOAPSFORMED IN SITU IN THE MINERAL OIL, THE ACID COMPONENTS OF SAID SOAPSCOMPRISING FROM ABOUT FIFTEEN PERCENT BY WEIGHT TO ABOUT EIGHTY PERCENTBY WEIGHT OF WOOL GREASE FATTY ACIDS AND THE BALANCE OF SAID ACIDCOMPONENTS COMPRISING ALIPHATIC ACIDS HAVING AT LEAST ABOUT TWELVECARBON ATOMS PER MOLECULE, THE METAL COMPONENTS OF SAID SOAPS BEINGSELECTED FROM THE GROUP CONSISTING OF LITHIUM AND LITHIUM, LITHIUM ANDSODIUM WITH THE MOLE RATIO OF LITHIUM TO SODIUM BEING BETWEEN ABOUT 15:1AND ABOUT 3:1, LITHIUM AND POTASSIUM WITH THE MOLE RATIO OF LITHIUM OFPOTASSIUM BEING BETWEEN ABOUT 50:1 AND ABOUT 10:1, AND LITHIUM AND TINWITH THE MOLE RATIO OF LITHIUM TO TIN BEING BETWEEN ABOUT 50:1 AND ABOUT8:1, PREFORMED SOAPS OF SAID MIXTURES OF LITHIUM-SODIUM,LITHIUM-POTASSIUM AND LITHIUM-TIN SOAPS COMPRISING A LITHIUM SOAP OFSAID ALIPHATIC ACID AND WOOL GREASE FATTY ACID SOAPS OF SAID METAL OTHERTHAN LITHIUM.